Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, video, and the like, and deployments are likely to increase with introduction of new data oriented systems such as Long Term Evolution (LTE) systems. Wireless communication systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, and other orthogonal frequency division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals (also know as user equipments (UEs), user terminals, or access terminals (ATs)). Each terminal communicates with one or more base stations (also know as access points (APs), EnodeBs, or eNBs) via transmissions on forward and reverse links. The forward link (also referred to as a downlink or DL) refers to the communication link from the base stations to the terminals, and the reverse link (also referred to as an uplink or UL) refers to the communication link from the terminals to the base stations. These communication links may be established via single-in-single-out, single-in-multiple out, multiple-in-single-out, or multiple-in-multiple-out (MIMO) systems.
A feature of interest in many communication systems is multimode operation. In multimode operation, communication devices, such as user terminals, may be configured to operate on different types of communication networks that use different Radio Access Technologies (RATs) and Radio Access Networks (RANs). In some cases, user terminals or other communication devices may be redirected from one RAN supporting a first RAT to a second RAN supporting a different RAT.
For example, some LTE networks may not support voice connections, or in some cases, an operator may wish to move a voice connection to another network under their control or coordination for various reasons, such as mobility, loading, or other reasons. In one case, in an LTE system, which is data-centric, an operator may wish to move a user attempting to make a voice call to another network that supports a different technology, such as a Circuit Switched (CS) connection. Alternately, the operator may wish to move a user receiving an incoming voice call. For example, the operator may wish to redirect a user from an LTE network and associated cells to another network, such as a UTRAN or GERAN network (e.g., a network that natively supports CS connections), using a procedure know as Circuit Switched Fallback (CSFB), which is described in, for example, 3GPP TS 23.272. In some cases, a user may wish to perform simultaneous voice and data communications, but redirection to other networks may create problems for simultaneous voice and data operation.